This invention relates to the art of anchoring devices, and more particularly to an anchoring device for securing a member to a relatively frangible wall accessible from only one surface thereof to provide an anchor holding an engaging element coupled to the member to be supported on the wall in a secure fashion with the anchoring device acting to strengthen the wall at the point of attachment.
A variety of situations exist in which it is desired to secure a member to a wall which does not normally have the requisite strength to securely engage a bolt, screw, or friction pin. Thus, with plaster walls, or walls formed of plaster board, sheet rock, fiberglass, or the like compositions, and even with many wood panelled walls, it is found that a screw, bolt, or nail will often not be retained securely when driven into the wall to hang mirrors, wall brackets, plaques, and the large variety of different hardware items which it is often desired to secure to a wall.
Accordingly, a variety of anchor bolts have previously been evolved for use in fastening an article to a "blind" opening in a wall, that is, an opening accessible from only one side of the wall. These anchor bolts have generally been either of a toggle bolt type or an expansible type.
In the toggle bolt type, two spring separated wings are secured to a nut, with the wings adapted for folding parallel to each other along an axis perpendicular to the plane of the nut. A bolt is engaged with the nut and the wings are folded against the bolt and the bolt with the wings folded thereagainst is inserted into the blind wall opening. The wings, after passing through the wall, expand and the winged nut is pulled up tight against the blind side of the wall by the bolt. This structure requires the fabrication and assembly of a multiplicity of parts, wings, springs, connecting pins, etc., and entails rather involved assembly.
Another type of toggle bolt, such for example as shown by applicant's prior U.S. Pat. No. 4,043,245, employs a toggle plate dimensioned to fit through the wall opening. This toggle plate must be held in some fashion against the blind side of the wall until an engaging element such as a bolt may be inserted into engagement with the toggle plate requiring a relatively complex multipart structure.
With the expansible anchoring device, a variety of plug members have been evolved for insertion into the wall opening, with a screw member engaging the plug, and expanding same as the screw is threaded into the plug to effect anchoring with respect to the wall. These expansion devices though relatively simple in manufacture and use, exert an undesired pressure on the wall opening often tending to crumble the surrounding area as they expand.